126 



On the Proboscis of the Fly. By B. T. Lowne, M.E.C.S. 



(Bead November 27th, 1868.; 



The Proboscis of the Blow-fly (musca vomitoria, Linn.) is one of 

 the most complex and remarkable structures in the insect world. 

 It is composed of a cbitiiious frame-work, or skeleton, invested in a 

 loose membranous integument, moved by a complicated system 

 of muscles, and largely supplied with air by numerous tracheal 

 tubes. 



The skeleton consists of parts homologous to all those usually 

 found in the mouths of insects, but some are so modified as only 

 to be recognised by studying other Diptera, and then, in order to 

 appreciate their true relations, it is necessary to examine specimens 

 which have not been subjected to pressure, but which have been 

 mounted with all their parts in their natural relations to each 

 other. 



Nearest to the oral cleft, and occupying the upper half of the 

 proboscis, is a large shuttle-shaped piece, serving for the attach- 

 ment of numerous muscles, exsertors, and retractors of the whole 

 organ, as well as semi-circular fibres enclosing the oesophagus ; — 

 which lies in front of — but in immediate contact with — the posterior 

 portion of this piece, which is hollowed out to receive it above, and 

 which completely surrounds it below, forming a corneous tube for 

 its protection. This may fairly be considered homologous to the 

 fulcrum in bees, or it may be looked upon as the mentum. 



Partially surrounding this, but closely connected with the integu- 

 ment, are two semi-circular bands of chitine, each bearing six to 

 eight stiff setse ; they support the large maxillary palpi, and repre- 

 sent the basal lobes of the maxillai of bees, the comb of which is 

 replaced by seta3 in the fly ; lower than these, and supported by 

 them are two thin, shield-like plates, covered with minute bristles 

 representing the small inner maxillary lobes of the Hymenoptera. 



These parts with their muscles enclosed in a loose integument 

 form the basal joint of the proboscis ; when at rest this is with- 

 drawn into the oral cleft, the fulcrum then rests in the cavity of the 

 head, and the membranous integument which is attached round the 

 oral cleft forms an inverted funnel, as far as the insertion of the 



